Comparison Between the Magnetic Irreversibility and Zero Resistance of High-Quality Melt-Processed YBaCuO Superconductors

This paper portrays a detailed study of the magnetic irreversibility limit T_irr (H) and of the zero resistance point T_c0 (H) of three different top-seeding melt-textured YBa₂Cu₃O_7−δ superconducting samples, with well-aligned c-axis and doped with a high density of nonsuperconducting Y₂Ba₁Cu₁O₅ (Y211) pinning centers. We have performed measurements for applied magnetic fields up to 140 kOe and for the whole set of the different field–current configurations. The magnetization measurements were performed using an MPMS-XL SQUID magnetometer and a vibrating sample magnetometer, both from Quantum Design. The electric transport measurements were made using a physical properties measurement system from Quantum Design. The goal of this exhaustive study is obtaining precise data about magnetic flux mobility along the various directions in the sample for the different field–current configurations, thereby defining the nature and effects, due to the strength and anisotropy of the pinning mechanisms and disclosing the various physical mechanisms dissipating electric transport in these systems below the superconducting transition temperature. We discuss our results in terms of the anisotropic flux pinning by the Y211 grains dispersed into the superconducting matrix.